Trolley electrical collector

ABSTRACT

An elongated metal trolley shoe has a groove in one side extending from end to end for receiving a trolley wire, with the opposite side of the shoe provided with threaded holes having their inner ends spaced from the groove. Screws in the holes for attaching the shoe to a support are made of a material that is at least as soft as the shoe, so that if the portion of the shoe originally separating its groove from the inner ends of the screws is worn away by a trolley wire, further wear of the shoe will occur in the same direction because the screws will wear at the same rate instead of forcing the wire to wear into the side of the groove.

United States Patent [191 Ross, Sr. Nov. 11, 1975 [54] TROLLEY ELECTRICAL COLLECTOR Primary E.\'aminerM. Henson Wood, Jr.

Assistant Eraminer-D. W. Keen 75 l e t Do i n or d R Ross Sr Pmsburgh Pd Attorney, Agent, or Firnz-Brown, Murray, Flick & [73] Assignee: U-S Safety Trolley Corporation, Peckham Pittsburgh, Pa.

[22] Filed: Nov. 7, 1974 [57] ABSTRACT [21] Appl. No.: 521,684 An elongated metal trolley shoe has a groove in one side extending from end to end for receiving a trolley wire, with the opposite side of the shoe provided with CCll l91/59I.;16,0L9;;gg threaded holes having their inner ends Spaced fro m [58] Field of Search IIIIIIIIIII 191/45, 46, 47, 48, 49, the groove. Screws 1n the holes for attach ng the shoe 191/50 59 59 l to a support are made of a material that is at least as soft as the shoe, so that if the portion of the shoe origi [56] References Cited nally separating its groove from the inner ends of the screws is worn away by a trolley wire, further wear of UNITED STATES PATENTS the shoe will occur in the same direction because the 2,830,138 4/1958 Monnery 19 l/5.9.l screws will wear at the same rate instead of forcing the wire to wear into the side of the groove.

3 Claims, 4 Drawing Figures US. Patent Nov. 11, 1975 TROLLEY ELECTRICAL COLLECTOR The electrical collectors that travel along trolley wires or rails take the form of either rotating wheels or sliding shoes. For industrial use, such as the collectors used with electric cranes, sliding shoes are practically always used. Such a shoe is provided with a groove that receives the trolley wire so that the shoe will stay on thewire. The shoe is made of copper or a similar good electrical conductor and, as it slides back and forth along the wire, the metal of the shoe is gradually worn away at the base of the groove. i

The shoe sold by one manufacturer is made from a bar of sintered powdered copper, with which graphite has been mixed to provide lubrication and reduce wear. The shoe is provided in the side opposite its groove with a pair of longitudinally spaced threaded holes,'in which there are screws that are used for attaching the shoe to a metal plate that is connected with an electric cable leading to a crane motor, electromagnet or other device that requires electricity to operate it. In the past, these screws have been steel. The inner ends of the screw holes in the shoe are spaced from the base ofthe groove.

copper. Although the conductor shown resembles a rail to some extent, it will be referred to .herein as a trolley wire 'since the invention disclosed herein can also be used with a round wire.- The illustrated wire has a head 1 and a foot 2 extending throughout its length and they are separated by a vertical web 3 that is integral with them. The wire issuspended from hangers (not shown) located at spaced intervals along its length. The foot of When such a shoe is installed, the maintenance peoof the groove. This wear often is allowed to continue until the worn side of the shoe becomes so thin that it breaks away and releases the shoe from the wire. The moment this occurs, the spring-pressed shoe support will extend and may strike the trolley wire or some other object and become bent or damaged, or it may swing to one side and cause a short circuit with a parallel trolley wire. In any case, if the shoe breaks away from the trolley wire, it is a very serious matter. Besides causing damage, it shuts down the crane. This may put several dozen men out of work until repairs can be made or, if the shoe is electrically connected to an electromagnet holding a'load of scrap metal for example, the scrap will be released and could seriously injure or kill anyone on whom it might fall.

It is an object of this invention to provide a trolley electrical conductor, in which any wear that occurs in the shoe after the trolley wire reaches the inner ends of the mounting screws will continue to be in a direction extending axially of those screws and not at an angle to them.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a fragmentary side view of a trolley conductor and guard, with part of the guard broken away to show the trolley shoe;

FIG. 2 is a vertical section taken on the line Il-Il of FIG. 1;

FIG. 3 is a reduced plan view of the shoe alone; and

FIG. 4 is a view similar to FIG. 2, but showing the shoe after it has been worn to a considerable extent.

Referring to FIGS. 1 and 2 of the drawings, an overhead trolley conductor of any desired length is formed of metal that is a good conductor of electricity, such as the wire projects from opposite sides of the web above it and has a transversely curved lower contact surface. The web of the wire spaces the foot far enough from the head to locate the foot a considerable distance beneath the upper portion of a tubular guard 4 that extends'along the wire, which it encloses to protect the wire from snow and ice and from accumulations of dirt. This guard is made of flexible rubber-like material and is supported by the wire. The bottom of the guard is split lengthwise throughout its length to provide it with lower edges that normally engage each other or overlap, whereby the wire is enclosed in a flexible tube.

Slidably mounted on the trolley wire inside the tubular guard is a trolley shoe 6. The shoe is-made from a bar of electrical conducting material, preferably sint ered powdered copper, with which graphite has been mixedThe upper side of the shoe is provided with a central longitudinal trough or groove 7 that extends throughout the length of the shoe. The lower portion of this groove is curved transversely to engage and more or less fit the curved lower contact surface'of the trolley wire, with the sides of the groove initially extending part way up the opposite sides of the wire. The groove guides the shoe as it is moved along the rail so that it cannot slide sideways away from the wire. The bottom side of the shoe is seated upon a flat plate 8 rigidly mounted on the upper end of a tubular plunger 9 that is urged upwardly at all times by a spring (not shown). Inside the plunger there is a copper rod 10, the upper end of which is joined to the plate and the lower end of which is connected to an electric cable that leads to the equipment that the current collected by the shoe is to operate.

The shoe is rigidly mounted on supporting plate 8 by means of a pair of screws 12 that extend up through openings in the opposite ends of the plate and into threaded holes 13 extending upwardly into the shoe. The upper or inner ends of these holes are spaced from the bottom of groove 7 in order to provide a body of metal between the bottom of the groove and the upper ends of the holes that can be worn away by the trolley wire before the holes and the: upper ends of the screwswill be exposed. When the holes are exposed, the shoe should be replaced by a new one because it has served its normal life, but it is a feature of this invention that if replacement does not occur at that time the shoe will continue to wear straight down for a considerable additional period of time as shown in FIG. 4, until it is clearly apparent that there is not much left of the shoe and that it will have to be replaced. Accordingly, the mounting screws are made of a metal that is at least as soft as the shoe metal, by which is meant that the screws will be worn away by the trolley wire asfast as, or at the same rate as, the shoe itself. The preferred metal for the screws is aluminum because it not only is softer than the shoe but it also is a good electrical conductor. Another screw material could be magnesium or zinc. Copper is not satisfactory when the shoe is made of powdered copper and graphite, because copper screws would be too hard and, like steel, would urge the trolley wire to one side or the other of groove 7 since the screws would resist wear more than the side wall of the groove.

If, for example, the original thickness of the shoe between the base of its groove and the bottom of the shoe is /8 inch and the screw holes are /3 inch long, the metal between the bottom of the groove and the upper ends of the holes will be inch thick. After this metal has been worn away, wear can continue straight down through the shoe for about another A of an inch, the upper ends of the screws being worn away in the process at the same rate as the shoe. Although this additional wear is not recommended, it results in the shoe lasting about twice as long as intended. Of course, the big advantage is that all of the wear is along the central vertical longitudinal plane of the shoe and does not extend off to one side, which would result in the side of the shoe breaking away and releasing the shoe from the trolley wire. The shoe disclosed herein, therefore, can avoid the damage to equipment that has occurred heretofore and can also eliminate the down time that results when a shoe breaks away from a trolley wire.

To prevent the top of the shoe at opposite sides of its groove from engaging the tubular guard above it when the groove starts to become deep, abrasive dressing devices, such as shown in U.S. Pat. No. 3,321,587, can be mounted on the trolley wire to grind down the top of the shoe as it travels back and forth across the dressing devices. The shoe is HO. 4 has been ground down in this manner.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a trolley electrical collector comprising an elongated metal shoe having a groove in one side extending from end to end of the shoe for receiving a trolley wire, the opposite side of the shoe being provided with longitudinally spaced threaded holes having their inner ends spaced from said groove, and screws in said holes for attaching the shoe to a support; the screws being made of a metal that is at least as soft as the shoe, whereby if the portion of the shoe originally separating said groove from the inner ends of the screws is worn away by a trolley wire, further wear of the shoe will occur in the same direction accompanied by wear of the screws at the same rate.

2. In a trolley electrical collector according to claim 1, in which said shoe is harder than aluminum, and said screws are aluminum.

3. In a trolley electrical collector according to claim 1, in which said shoe is made from a mixture of sintered powdered copper and graphite, and said screws are alu- 

1. In a trolley electrical collector comprising an elongated metal shoe having a groove in one side extending from end to end of the shoe for receiving a trolley wire, the opposite side of the shoe being provided with longitudinally spaced threaded holes having their inner ends spaced from said groove, and screws in said holes for attaching the shoe to a support; the screws being made of a metal that is at least as soft as the shoe, whereby if the portion of the shoe originally separating said groove from the inner ends of the screws is worn away by a trolley wire, further wear of the shoe will occur in the same direction accompanied by wear of the screws at the same rate.
 2. In a trolley electrical collector according to claim 1, in which said shoe is harder than aluminum, and said screws are aluminum.
 3. In a trolley electrical collector according to claim 1, in which said shoe is made from a mixture of sintered powdered copper and graphite, and said screws are aluminum. 